


A Brother's love

by FelliSkelli



Category: Underfell - Fandom, Undertale
Genre: M/M, Masturbation, heat - Freeform
Language: English
Status: Completed
Published: 2017-07-06
Updated: 2017-07-06
Packaged: 2018-11-28 11:01:58
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,718
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11416566
Author URL: https://archiveofourown.org/users/FelliSkelli/pseuds/FelliSkelli
Summary: Sans is at his sentry station, just starting his first heat, and his mind is overcome with thoughts of his little brother....but surely Papyrus would never feel the same?





	A Brother's love

Everyone knew that the Underground ran on LOVE.

No one would deny that Underfell was was a vile, harsh place to live; kill or be killed was the motto everyone lived by. Children were a rarity...but even they were barely protected by King Asgore’s fury over any death of a child. 

It was ugly too; dingy, filthy and cold and far too empty. Not just Snowdin, but Waterfall and Hotlands too. The entire monster population rattled around in a space that could have held a hundred times their number. It was tragic really...and depressing.

It seemed that soon, the partial genocide enacted by the humans centuries ago would be finalized by the monsters themselves.  And it was not simply their more violent natures that would lead to their extinction either. Starvation was a reality, especially in Snowdin, so far from the capital that it was half forgotten in the rush to find food for the waning population.

And it was certainly not fit for the soft hearted, the lazy, the weak. 

So how had Sans the skeleton survived so long? 

With only 1 hp...he should have been dusted for his EXP long ago. 

If it wasn’t for his little brother Papyrus, he would never have survived so long. Papyrus was  _ amazing _ . Lieutenant of the Royal Guard under Captain Undyne. Fierce, no nonsense, bossy, demanding and absolutely in control of every aspect of Sans’ life.

Sans sighed and took another swig of mustard as he contemplated his brother for the umptempth time that day and shifted restlessly on the stool. He just couldn’t stop thinking about how insanely lucky he was. Papyrus was coolest, strongest and most fearsome monster in the whole underground! No one dared cross him, or do anything to draw his attention.

Well...after the king of course. And Undyne...if he had to be honest. She scared the piss out of him. 

But other then those two, Papyrus was the best!

Sans didn’t deserve him. He knew that. He was a lazy, no good piece of shit...why did Papyrus even bother with him?!

No one else seemed to care a bone shard for him...not even himself. He was well aware that he was a huge disappointment, a failure of a creation and nothing but a listless burden on his brother’s broad shoulders. 

He knew that his brother’s strange attachment to him confused others...the Dogs mocked him constantly for holding his brother down...and Undyne made no secret her disgust with his very existence.

He shifted again on the stool, growling softly in disgust as he felt a strange moistness in his pelvis.

While Sans had always admired his brother, always been so dang proud of him, lately he’d been thinking of Papyrus in more….intimate ways. Sans knew he’d do anything for Papyrus...now he wanted to do  _ anything _ to him. Just wanted to make him feel good. He’d found his eye lights drifting to Papyrus’ hips when he walked, or watching his mouth as he ate. 

And his dreams…

Usually he was kept up by nightmares of the void, but lately the dreams had been much more pleasant...physically at least.

He was so sick. He sighed again, trying to ignore the growing heat in his pelvis. It had been irritating him all day...an itch in his bones, a heat in his marrow. He felt like he was going to combust. 

And he  _ ached _ .

He pulled his hood over his skull, trying desperately to distract himself by staring at the disturbed snow in front of his station, but nothing was moving, not even the trees; there was not even a hint of wind to bring him relief as his bones burned.

He whined weakly, leaning one arm on the shelf of his sentry station, burying his skull in the crook of his arm as he gave into the burning need in his bones. He ran one shaking hand over his fragile ribs, biting back a gasp as pleasure sparked straight to his pelvis. His soul was glowing through the thin shirt he wore beneath his open hoody, his pelvis glowing through his shorts as his magic began to coalescence. 

He bit back a growl and rubbed harder, scraping over his sternum and reaching beneath his shirt to feel the scrap of bone-on-bone as sweat began to bead his skull, his left eye light aglow with a bright crimson flame. But while his ribs felt good...he needed the friction elsewhere, and before he could talk himself out of it he had shoved his hand beneath the band of his shorts and was rubbing furiously at his pubic symphysis, small desperate whimpers falling past parted teeth.

Sans had never really been one for masturbation, but when he had on the rare occasion indulged in the release of an overabundance of magic he’d usually just gone with a cock, it was quicker to deal with. But right now he was trusting frantic phalanges into the solidifying mass of magic, pumping fast and hard, and a slick cunt formed around his fingers, clenching tight and trying to pull his short fingers deeper.

He only wished it was someone else's hand…

“ _ Papyrus…” _ he whimpered.

Oh...his brother was so big and strong with his sturdy, heavy bones...he’d give Sans the pounding he so desperately needed...he was thrusting hard with three phalanges now, his thumb scraping with a bruising force over his pubic symphysis, almost able to imagine it was his brother’s hand. His slick, red arousal hand sopped past his thin boned hand, soaking his boxers as his hand made lewd squelches every time he thrust deep.

Would Papyrus insult him while fucking him senseless? Or would he say sweet nothings...oh, he would be so rough, Sans would be bruised and bitten all over…! Marked and claimed for all to see!

Sans completely forgot where he was, moaning shamelessly loud as he rode his hand as hard as he could, crying out his passion, sobbing for his brother to relieve him of his aching need. He threw his head back with a keening cry, he was so close...so close…

“Well...what have we here…? A little bitch in heat?” a rough voice growled with amusement and lust.

Sans froze. The heat in his marrow chilled as the ice of fear washed over him. He blinked slowly, breathing heavily as he fought to remain calm and not simply flee. He knew he could outrun any of the dogs….he would take a short-cut if he had to, but none of them knew about that ability...not even Papyrus. He’d rather not out himself just yet…

He had nothing to fear...the dogs were loyal to Papyrus he told himself nervously as he finally focused his blurry vision on Doggo, the buff stillness-blind dog slouching with his paws in the pockets of  his jeans, his usual biscuit held in his teeth as he leered at Sans in a way that had him shrinking back into his hoody. 

That was when he realized his hand was still in his pants and he yanked his phalanges out of himself with a loud squelch that had Doggo begin to drool as he started stalking towards him with deadly intent. “W-what do you think you--...don’t you have work to be doing?” Sans growled, but it came out with a more nervous stutter than he had intended and he almost fell off his stool as Doggo slammed his large paws on the sentry station and leaned towards him. 

“Something smelled good, so I came to investigate...imagine my surprise when I found out it was you!” Doggo explained while his dark eyes seemed to drill into Sans’, which was absurd, he was sitting still… “Look at you...so needy...you’re shivering so much I can see you clearly!” The dog continued smugly. “If you beg nice enough maybe I’ll help you out…” he taunted as he began to reach for Sans.

Sans swallowed thickly and was about to snap back that it was none of Doggo’s business when he heard Papyrus from the distance,

“DOGGO, GET THE  _ FUCK _ AWAY FROM MY BROTHER.” 

Sans had never heard his brother swear before but he could not help the grateful whimper he made as he looked up at the furious guardsman, staring at Doggo with a scowl that was just daring the dog to test him. His eye lights were glowing a deadly scarlet, washing his skull in red, and in his hand was his usually bone cudgel. He meant what he said. Doggo indeed scowled and straightened up to glower at the younger of the skeleton brother’s, but when Papyrus sent a wave of bones at his feet he yelped and slunk back into the forest with his tail between his legs and swearing beneath his breath.

Sans stared silently at his savior as his brother stomped across the clearing towards him and yanked him off of his stool and into his arms. Sans gasped and clung to him, flushing crimson clear down to his clavicles. 

“WHY DIDN’T YOU TELL ME YOU WERE IN HEAT, YOU IMBECILE?” Papyrus reprimanded him coldly as he turned and began walking briskly, apparently to carry Sans to their home. Sans sputtered, flushing darker and shrugging weakly.

“I didn’t know, I’ve never been in heat before, boss...and why would you care--I mean...why would you even...it’s gross that...I...mean...I’m so worthless and…” he muttered weakly, dropping his eye lights in shame and digging restlessly at the scar bisecting his right eye socket. He really hadn’t noticed at first; he had been hungover (again) and had nightmares (again.). He never did sleep very well.

“IDIOT. WHO ELSE WOULD TAKE CARE OF YOU BUT I, THE FEARSOME AND TERRIBLE PAPYRUS?” his brother snarled, impatient with his self-deprecation. Sans flinched and nodded weakly, trying not to cry. Papyrus, ever perceptive, paused mid-step and glanced down at Sans, brow bones furrowed. “YOU AREN’T ABOUT TO  _ CRY _ NOW, ARE YOU?” he sighed in disgust and Sans burst into tears of shame.

“I-I’m so...sorry for being a burden! I...I just can’t do  _ anything _ right and now you have to deal with how gross I am…” he gasped, clutching to his brother even as he just wanted to crumble to dust. 

Papyrus’ teeth twisted in a snarl of disgust before something flickered in his eye lights and he sighed. He glanced around as though making sure that they were alone before lifting Sans up and clanking his teeth to his skull in a skeleton-kiss. “HUSH, STUPID. YOU AREN’T GROSS, OR A BURDEN. IF YOU HAD NOT WORKED YOURSELF...TO THE  _ BONE _ ...WHEN I WAS A BABYBONES...I WOULD HAVE DIED...LET ME TAKE CARE OF YOU BROTHER…” Papyrus murmured to him, and Sans was equally taken aback by the pun as he was by the sentiment. He gaped up at his brother, eye sockets wide. “HEH...IS THAT WHAT IT TAKES TO FINALLY SHUT YOU UP FOR ONCE, BROTHER?” Papyrus said, almost teasing. 

Sans just flushed even darker and raised one hand to tentatively stroke his brother’s cheek. “B-boss...Paps...I...I love you…” he admitted weakly, the words that had been weighing on his soul for what seemed like ages now. Papyrus rolled his eye lights as though that was the most obvious statement in the world.

“OF COURSE YOU DO.” He scoffed arrogantly before leaning down to clack his teeth to Sans’. “I LOVE YOU TOO.” he added more gently, and Sans’ soul nearly exploded as he clung to his brother with a sob of joy.

“COME BROTHER, LET ME TAKE CARE OF YOUR HEAT…” Papyrus purred and continued to carry his brother home.

Sans moaned against his brother’s neck, his heat having returned with a vengeance now that Doggo was chased off and his brother’s intentions made clear. He needed Papyrus.  _ Now. _ He chuckled and leaned back to give his brother a mischievous grin. “That’s ok, Pap...I know a short-cut.” he declared as he concentrated with the last of his focus and brought them just inside the door of their home.

Papyrus stumbled, eye sockets wide and he gaped for a moment before regaining his dignity. He gazed down at his brother in a way that made it clear that they would be having a long discussion in the future, but thankfully Papyrus seemed more interested in Sans’ dripping need then in interrogating him. He made sure the front door was shut and locked with a glance over his shoulder before immediately stomping  across the living room, up the stairs, and into his room, slamming the door shut with one foot while tossing Sans onto his bed.   
  
Sans landed with a grunt and sat up to berate his brother for his rough treatment when the words caught in his throat as he watched Papyrus stripping out of his battle-body with rough efficiency. He blinked, flushing anew as he wiggled and nearly fell off the bed in his eagerness to follow suit. He simply shrugged out of his hoody and nearly tore his shirt off before yanking at his shorts, tripping as he forgot to take off his shoes first.

Papyrus had already removed his scarf, gloves and shirt by this point and he lunged forward to catch Sans with an impatient growl that sounded half a laugh. “ARE YOU SO ANXIOUS, BROTHER?” he teased huskily as Sans clutched at his forearms and looked up at him, hungry and desperate. To his relief there was  a similar heat in his brother’s gaze as Papyrus’ eye lights slid from his skull down to his ribs and the glow still emanating from his shorts. He licked his teeth slowly, and the sight of the dark red magical appendage had Sans’ knees collapsing beneath him and he made a desperate whine behind his teeth.

Papyrus had never seen Sans without his bulky clothing before, not even when they were both young, he had not realized how  _ delicate _ and fragile Sans was. He growled softly and sat Sans much more gently on the bed before kneeling to remove his shoes, ignoring Sans’ sputtered complaints. “SANS.” he hissed warningly. 

Sans was mercifully silent and Papyrus hummed with satisfaction as he removed Sans’ shoes and socks, and then his shorts, leaving him just in his his absolutely sodden boxers. Papyrus paused then to stare, while Sans flushed down his ribs and moved his hands to cover himself, feeling ashamed all over again. Papyrus caught his wrists easily and kept staring before smirking up at Sans in a predatory manner which had him moaning with need. “YOU ARE SUCH A MESS, BROTHER…” he teased. He released Sans’ hands so that he could remove that last barrier to his hungry gaze, and when he saw Sans’ puffy and slick pussy he licked his teeth again with a low, almost feral growl that had Sans tingling down to his toes. 

“P-Paps... _ please… _ ” Sans begged. Papyrus chuckled and leaned forward to inhale his scent greedily. 

“YOU ARE ALMOST CUTE WHEN YOU BEG, BROTHER…” he purred. “BEG MORE.” he added as he gripped Sans’ hips with an almost bruising force and dove down to lick a stripe up his puffy outer lips. Sans wailed, clutching at Papyrus’ skull and bucking beneath him.

“P-Papyrus! PLEASE! Please, please!” he begged. Oh, he was burning up! Papyrus was just teasing him!

Papyrus seemed satisfied with his efforts and buried his skull between Sans’ spread femurs, thrusting his tongue hungrily inside Sans’ dripping cunt and slurping lewdly while Sans squealed and moaned above him. “HMM. YOU TASTE GOOD, BROTHER.” Papyrus declared as he pulled out, ignoring Sans’ wail of distress. He licked his teeth with satisfaction, looking rather smug as he shoved Sans back to lay prone. “BUT THERE IS TIME FOR SUCH NICETIES LATER. YOU NEED SOMETHING MORE NOW, DON’T YOU…?” He purred as he slowly undid his belt, going far too slow for Sans’ liking. 

He could see the bulging tent in his brother’s shorts. The red flush to his brother’s bones. He whimpered and rolled over onto his hands and knees, presenting like a bitch in heat to his brother. “OH...STARS SANS….” Papyrus swore, voice deep and wavering just slightly. Sans heard his belt snap, heard his pants coming undone, the thud of his boots being dropped to the floor and then being followed by his pants. He had not even taken the time to fold them!

The bed creaked as Papyrus climbed up behind him, stroking his hands gently, almost reverently over Sans’ ribs and spine, tracing all the little scars and cracks while Sans whimpered beneath him. Papyrus seemed as though he would simply continue to tease Sans until he lost his mind, but after a moment he reached down to grip Sans’ hip with one hand, lining his cock up with Sans’ entrance with the other. “NYEH NEYH NEYH….I AM GOING TO WRECK YOU NOW, BROTHER...ARE YOU PREPARED?” he declared smugly.

“Yes, oh stars, yes! Please! I need---” Sans’ breathless response transitioned into a high, keening wail as Papyrus slammed into him, straight to the hilt with one snap of his powerful hips. 

“GOOD, BROTHER….NNN...CRY FOR ME!” Papyrus snarled as he slowly pulled almost all the way out before slamming back in. Sans clutched at the comforter beneath them in trembling hands, crying out in delight as the dreadful heat in his pelvis was finally given some relief. His brother’s cock was wider and longer than the one he summoned for himself, and it filled him almost painfully, almost hitting his spine above his coccyx every time he slammed home. Sans’ magic stretched easily around the thick girth however, and he had no complaints for his brother’s technique.

A small part of his mind wondered where his brother had learned to talk so dirty, to fuck like this…

But now was hardly the time to dwell on such things. 

\---

Papyrus was currently doing his absolute best to make Sans cry himself hoarse, driving him into the mattress with every slam of his hips, the bed creaking beneath them. Sans was incoherent by this point, face and shoulders against the mattress while he drooled helplessly, eye lights blown out with lust as he moaned continuously.

Papyrus himself was looking a little flushed as he rode his brother, snarling softly as he made sure to pace himself, not wanting to be too rough on his more delicate brother, but also determined to give him what he needed to drive the heat from his bones. Also, the debauched look on his face was very appropriate for him. Papyrus rather liked it. He would strive to see that expression on him more often. Is was so much better than that sullen, sulky look he often had. Or when he looked so exhausted after a nightmare...Papyrus shifted his hand to reach around to pinch his brother’s clit, eliciting a beautiful howl of delight as the tight sheath around his cock clenched tight and with a small wail, Sans came, pussy rippling as though trying to milk his cock. 

Papyrus grunted as Sans’ little pussy clenched like a vice around him, panting softly as he fought through the tightening muscles to pump just twice more before releasing his load, deep inside his brother. He watched with satisfaction as the deeper red of his magic glowed beneath his brother’s translucent ectoplasmic body, a small tummy forming to hold all his cum. He wondered if it would give his brother strength...he smirked at the thought. Maybe he would feed Sans his cum on a regular basis...it would surely be better for him than that mustard he guzzled.

Sans had collapsed beneath him with a low, drawn out moan, smiling blissfully up at Papyrus and his soul swelled with satisfaction to see his brother look so satiated. He slowly pulled out of him, a little disgusted by the mess, but willing to overlook it for the moment. He scooped Sans into his arms and then shifted to lay him properly across the bed before crawling in to join him, to his brother’s utter astonishment.

“P-pap?” Sans stuttered softly, looking confused. Papyrus sighed. He knew he had been more stern with Sans recently than he really ought to have been (heck, he’d been outright cruel at times), but he’d been frustrated with his need to claim Sans, and with rising through the ranks of the Royal Guard to gain the reputation to protect them both...and he took his short temper out on the only target he had, which was Sans.

He clanked his teeth to Sans’ forehead and pulled him close. “YOU WILL SLEEP HERE WITH ME FROM NOW ON.” he declared, his tone not brooking any argument. Sans looked taken aback, but also a little shyly pleased by such an order, however he still seemed to insist on arguing over every little thing. He was so aggravating sometimes!

“Ah...y-yes Boss…! But…” Sans agreed, stuttering slightly before Papyrus cut him off.

“NO ‘BUTS’ SANS.” he hissed, pulling a blanket over the both of them. “NOW GO TO SLEEP, THAT SHOULD BE EASY FOR YOU.” He growled and pulled Sans close, closing his eyes to sleep with him. He knew Sans’ heat would need a little more rounds before it was satisfied. He wanted to conserve his strength. Sans did not argue again, but did cling to him in a rather endearing way.

“I love you Papyrus…” Sans said sleepily as he nestled trustingly close. Papyrus smiled softly, stroking his brother’s skull gently.

“I LOVE YOU TOO...SANS.” he replied.

\--

“Boss…?” Sans panted as he rode Papyrus’ cock like the cute little slut he was. Papyrus grunted in response, intent on watching his cock be engulfed by Sans’ hungry little pussy. 

“Where did you….learn to talk like that?” Sans asked shyly, moaning every time he shifted his hips, driving Papyrus’ cock in just right to hit his g-spot.  
  
“THE WALLS ARE THIN SANS...AND YOU TALK IN YOUR SLEEP.” Papyrus responded smugly. 

Sans sputtered furious denials, but Papyrus remained smugly assured that Sans had wet dreams about him often.

The Underground ran on love after all.


End file.
